In recent years, a transition of an X-ray diagnostic imaging apparatus is currently in progress, from a type employing an image intensifier (hereinafter, abbreviated as “I.I.”) as its X-ray detector, to a type employing a flat panel detector (hereinafter, abbreviate as “FPD”). This is because, the FPD facilitates reduction of a visual sense of oppression relative to the I.I., and the FPD has a wide dynamic range without distortion, enabling acquisition of favorable image quality.
The I.I. type mobile X-ray apparatus is still dominant, but currently the FPD type is being introduced into the market. Since it is expected that the FPD type is introduced more in the future, it becomes indispensable to address a technical problem which is caused by the mobile X-ray apparatus of the FPD type.
In the mobile X-ray apparatus, when a C-shaped arm supporting both X-ray radiographic equipment and the X-ray detector being arranged in such a manner as opposed to each other, places therebetween a portion of interest of a test subject (positioning the C-shaped arm with respect to the portion of interest is performed without interference with the test subject nor a bed on which the test subject is placed), since there are a wide variety of portions of interest and operative methods, variations are found such as a standing position of an operator and arrangements of peripheral equipment. Positioning of the mobile X-ray apparatus and an inserting direction of the C-shaped arm are required to be responsive to each of those variations. In other words, in many cases, the C-shaped arm is subjected to constraints that it has to be inserted from a position and in a direction so as not to be an obstacle to the operator and the peripheral equipment. One of the problems caused by the inserting direction is that the orientation of an image displayed on the display device, that is, the orientation of the portion of interest is not kept constant.
The operator carries out a diagnosis viewing the image displayed on the display device. Therefore, in order to avoid erroneous diagnosis and facilitate recognition of the portion of interest, it is necessary to display the portion of interest constantly in the same orientation within the X-ray image displayed on the display device (e.g., the body axis direction of the test subject is made to be in line with the longitudinal direction of the display, and the head of the portion of interest is made to be directed upward in the display), or it is alternatively necessary to display the portion of interest in a desired orientation.
However, the inserting direction of the C-shaped arm is different in each case, and also the portion of interest in the X-ray detector (X-ray incidence plane) supported by the C-shaped arm and the orientation thereof with reference to the body axis direction are different in each case. Therefore, in order to keep the portion of interest to be in the same orientation constantly, it is necessary to correct tilt of the portion of interest.
As a suggestion to address this problem, for example, the Patent Document 1 discloses a technique for mechanically correcting the rotation of a video system, such as a TV camera and TV deflection coil, in the I. I. type X-ray diagnostic apparatus. The Patent Document 2 discloses a technique for rotating the FPD to reserve a proper effective field of view, and also rotating the display device itself for displaying an image of the test subject, so as to allow the test subject to be in a desired orientation.